The present invention generally relates to a self-supporting motor vehicle body, and more particularly to a self-supporting motor vehicle body for increasing the body strength of a motor vehicle against torsinal vibrations about a longitudinal axis of the vehicle.
Self-supporting bodies of this type are familiar from the series production of motor vehicles and are disclosed, for example, by German Published Unexamined Patent Application (DE-OS) 2,847,679.
Meeting stability and safety requirements on motor vehicles, motor vehicle bodies typically comprise lateral, front and rear side members, although these members cannot merge into one another in a straight line since the front and rear side members have to be set back towards the middle of the vehicle in front of the wheel installation space. The resulting bent connection of the side members to one another means that, the stabilization of the body, especially on open vehicles lacking a roof which increase rigidity, is too low against torsional vibrations about a longitudinal axis of the vehicle. As a consequence of this, motoring comfort is impaired since the torsional vibrations generated during motoring are experienced by the vehicle occupants as so-called cross-jolting.
An object on which the present invention is based is to increase the body strength of a motor vehicle against torsional vibrations, thereby reduce the extent of the maximum torsional vibration amplitudes and increase the natural torsional frequency value of the body and consequently set it further apart from the natural torsional frequency of the wheels and wheel axles.
These and other objects of the present invention are achieved by providing struts aligned and secured to the body substructure in such a way that the torsional amplitudes of the body are reduced and that the torsional stability of the body is increased or its natural torsional frequency rises into a range several Hertz higher.
This arrangement assures that the torsional vibrations occurring during motoring are perceived by the vehicle occupants to a far lesser extent, and that the higher stability of the body has a more beneficial effect on built-in fittings, such as, for example, a front windscreen. This solution for an improvement of stability is expedient, above all, for motor vehicles without a fixed roof. It is likewise advantageous that the higher natural torsional frequency of the body is now further above that of the wheels together with their wheel axles, so that the body is not additionally excited by the vibrations of these structures.
With an alignment of the struts at approximately 45.degree. relative to the longitudinal axis of the vehicle, the effect of the strut of supporting a dynamically changing tensile and compressive load is at its greatest. If a strut were possibly aligned in a longitudinal direction of the vehicle, it would be subjected, above all, to bending stress as a result of a likewise occurring transverse movement of the forward structure or rearward structure in relation to the passenger cell and would therefore have to be designed for a higher load, whilst a strut aligned in the transverse direction of the vehicle is far less effective for increasing the stability.
For a strut according to preferred embodiments of the invention, therefore, it is sufficient to profile the strut in such a way that it withstands a dynamic tensile and compressive load and that it can be matched especially simply to the prevailing conditions of the substructure.
The struts perform their function in the region of both the forward structure and the rearward structure, increase the torsional stability diminished by the bending of the front and rear side members in relation to the lateral side members and reduce the transverse movement of the forward structure and of the rearward structure relative to the stable passenger cell.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.